This invention relates to a nut former, more particularly to a durable driving apparatus for activating a workpiece impelling mechanism in a nut former which has a simplified construction.
Referring to FIG. 1, a nut former includes basically a flywheel (A), a punch unit (B), a die unit (C), a workpiece gripping and conveying unit (D), a feeding unit (E), a cutting unit (F), a workpiece impelling mechanism (G) and a discharge unit (H). In mass production under automatic control, an elongated metal material is moved by the feeding unit (E) to a position in which the metal material is cut off to form a workpiece of a predetermined length to be forged. Then, the workpiece is moved by the workpiece gripping and conveying mechanism (D) to another selected position in which the punch unit (B) forces the workpiece into the die unit (C). Finally, the workpiece impelling mechanism (G) impels the workpiece out of the die unit (C). The workpieces are collected in the discharge unit (H).
Referring to FIG. 2, when a driving shaft (I1) is activated, a driving apparatus (J) rotates the rotating shaft (G1) of the workpiece impelling mechanism (G) in alternate clockwise and counterclockwise directions so as to impel workpieces out of the die unit (C) by the push rods (G2) of the workpiece impelling mechanism (G).
Referring to FIG. 3, a conventional driving apparatus (J) includes a cam member (J1) sleeved rigidly on the driving shaft (I1), and a V-shaped crank (J2) having a first crank arm (J21) carrying a cam follower (J22) thereon, which is arranged in association with the cam member (J1), and a second crank arm (J23) pivoted to the left end of a link (J3). A swing arm (J4) is sleeved rigidly on the rotating shaft (G1) of the workpiece impelling mechanism (G) at the lower end thereof and connected pivotally to the right end of the link (J3). A resilient means (J5) includes a tension spring (J51) secured to the link (J3) by a coupling (J31) at the left end thereof. The right end of the tension spring (J51) is secured to the nut former so as to pull the second crank arm (J23) to the right, thereby maintaining the engagement between the cam member (J1) and the cam follower (J22). As a result, the rotation of the driving shaft (I1) is converted into the reciprocal movement of the push rods (G2). The driving apparatus (J) suffers from the following disadvantages:
(1) When the periphery of the cam member (J1) is severely worn, the cam member (J1) must be replaced so as to ensure the precision of the nut former. It is necessary to remove and mount a large number of elements, such as an equilibrium mechanism or counterweight, during the replacement process of the cam member (J1). PA0 (2) Because the driving apparatus (J) consists of many parts, it is easy to make a great deal of noise in operation. PA0 (3) High-speed mass production of nuts easily causes fatigue of the tension spring (J51). As a result, the cam follower (J22) cannot closely contact the cam member (J1). PA0 (4) Stress easily concentrates on the pivots between the crank (J2), and the link (J3), and between the link (J3) and the swing arm (J4), resulting in deformation of the pivots.